The composition of Thorianite, and the relative Radio-activity of its constituents

[Prefatory Note by Sir William Ramsay .—When the cubical mineral from Ceylon, sent to me by Mr. Holland in December, 1903, and named by Professor Dunstan “Thorianite,” was analysed by several of my students, it was evident that although in the main, as shown by the analysis made by Mr. G. S. Blake under Professor Dunstan’s supervision, it consisted of the oxides of thorium and uranium, its composition is by no means simple. The analyses referred to were made by Dr. R. D. Denison, by Mr. Gimingham, and by Mr. Le Rossignol; they are as follows (for convenience of reference Mr. Blake’s analyses are also appended) :— The extraction of radiothorium by Dr. O. Hahn, and various other investigations carried on in my laboratory, made it evident that under the heading “lead,” for example, various other metals were included, and Dr. Büchner undertook to carry out an analysis on a larger amount, so as to ascertain what elements were present in the analytical groups into which, the constituents of the mineral had been roughly divided by previous analysts. Another of the objects of his research was to determine how the radio-activity of thorianite is distributed over its various constituents. Assuming, as looks more than probable, that the radio-active constituents of thorianite, like those of similar radio-active minerals, are in process of change, it is to be expected that by working on comparatively large quantities these bodies and their products can be identified, even though in themselves they may not display the property of radio-activity.]